Java Lambda Expression Runnable Example

This post shows how to implement Runnable interface as a lambda expression when you are creating a thread in Java. Since Runnable is a functional interface, Java 8 onward it can also be implemented as a lambda expression.

Refer Lambda expressions in Java 8 to know more about Java lambda expressions.

It is very common to implement the run() method of Runnable interface as an anonymous inner class, as shown in the following code.

Runnable as an anonymous class

public class RunnableIC {
  public static void main(String[] args) {
    // Runnable using anonymous class
    new Thread(new Runnable() {
      @Override
      public void run() {
        System.out.println("Runnable as anonymous class");
      }
    }).start();      
  }
}

From Java 8 same can be done with lambda expression in fewer lines increasing readability, as shown in the following code.

Runnable as a lambda expression in Java

public class RunnableLambda {
  public static void main(String[] args) {
    // Runnable using lambda
    new Thread(()->System.out.println("Runnable as Lambda expression")).start();
  }
}

If you want to make it more obvious then you can also write it as below.

public class RunnableLambda {
  public static void main(String[] args) {
    Runnable r = ()->{System.out.println("Runnable as Lambda expression");};
    // Passing runnable instance
    new Thread(r).start();
  }
}

That's all for this topic Java Lambda Expression Runnable Example. If you have any doubt or any suggestions to make please drop a comment. Thanks!

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1. Java Lambda Expression Comparator Example
2. Java Lambda Expression Callable Example
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4. How to Fix The Target Type of This Expression Must be a Functional Interface Error
5. Java Lambda Expressions Interview Questions And Answers

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